Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-08-07
2003-01-14
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S414000, C528S111000, C528S405000
Reexamination Certificate
active
06506821
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to self-dispersible curable epoxy resins based on epoxy/amine adducts, to a process for their production and to the use of these special epoxy resins for coating solid substrates.
For many years, curable epoxy resins have been used as components in coating compositions. However, the properties of coatings produced using aqueous epoxy resin dispersions have long been considered inferior to those of coatings in which the resin is used in the form of a solution in an organic solvent. This was mainly attributed to the fact that the emulsifiers used, for example nonylphenol ethoxylates, migrate to the surface of the film where they adversely affect its properties. One way of solving this problem is to use so-called reactive emulsifiers which, where the epoxy resin is crosslinked with a diamine or polyamine or other hardener, react with the hardener and thus become part of the coating. Aqueous dispersions of special reactive emulsifiers are known from the prior art.
U.S. Pat. No. 4,315,044 describes a stable epoxy resin dispersion containing (1) an aqueous medium and (2) between 50 and 70% by weight of a self-emulsifiable epoxy resin which is the addition product of (a) 40 to 90% by weight of diglycidyl ethers of a dihydric phenol, (b) 5 to 35% by weight of a dihydric phenol and (c) 2 to 15% by weight of the diglycidyl ether of a polyoxyalkylene glycol and in which the molecular weight of the epoxy resin is between 500 and 20,000.
U.S. Pat. No. 4,608,406 describes a stable epoxy dispersion containing (1) an aqueous medium and (2) between 50 and 70% by weight of a self-emulsifiable epoxy resin with a molecular weight of 1,000 to 20,000 which is the addition product of (a) 40 to 90% by weight of diglycidyl ethers of a dihydric phenol, (b) 5 to 35% by weight of a dihydric phenol, (c) 2 to 15% by weight of the diglycidyl ether of a polyoxyalkylene glycol and (d) 2 to 15% by weight of an alkyl phenol/formaldehyde
ovolak resin.
EP-B-272 595 and DE-A-36 43 751 describe a process for the production and use of stable aqueous epoxy resin dispersions consisting of a) 50 to 80% by weight of an epoxy compound containing at least two epoxy groups per molecule and having an epoxy equivalent weight of 100 to 2,000, b) 35 to 17% by weight of an aromatic polyol and c) 15 to 3% by weight of a condensation product of an aliphatic polyol with a molecular weight (Mw) of 200 to 20,000 and an epoxy compound containing at least two epoxy groups per molecule and having an epoxy equivalent weight of 100 to 2,000, the equivalent ratio of the OH groups to the epoxy groups being from 1:0.85 to 1:3.5 and the epoxy equivalent weight of this condensation product being from 200 to at least 50,000.
WO 95/18165 (Henkel Corp.) describes a self-dispersible curable epoxy resin obtainable by reacting an epoxy resin (a) with a polyoxyalkylene amine (b) with a molecular weight of 3,000 to 15,000. The components mentioned are used in a ratio of (b) to (a) of 0.001:1.0 to 0.060:1.0 equivalent.
WO 96/20971 (Henkel Corp.) describes a self-dispersible curable epoxy resin obtainable by reacting (a) 1.0 equivalent of epoxy resin, (b) 0.01 to 1.0 equivalent of a polyhydric phenol and (c) 0.005 to 0.5 equivalent of an amine/epoxy adduct. The amine/epoxy adduct is a reaction product of 1.0 equivalent of a polyepoxide and 0.3 to 0.9 equivalent of a polyoxyalkylene diamine.
EP-A-747 413 describes a self-emulsifiable epoxy resin (A) obtainable from (A-1) 50 to 95% by weight of one or more epoxy compound(s) containing at least two epoxy groups per molecule and having an epoxy group content of 300 to 11,200 mmoles/kg, (A-2) 5 to 50% by weight of an aromatic polyol, (A-3) 0 to 25% of modifying compounds containing at least two epoxy-reactive groups, (A-4) 5 to 35% of a condensation product—acting as emulsifier—of (A-4-a) an aliphatic polyol with a weight average molecular weight M
w
of 200 to 20,000 g/mole and (A-4-b) an epoxy compound containing at least two epoxy groups per molecule and having an epoxy group content of 500 to 10,000 mmoles/kg, the ratio of the number of OH groups to the number of EP groups being from 1:2 to 1:10 and the epoxy group content of the condensation products (A-4) being from 100 to 6,700 mmoles/kg.
DESCRIPTION OF THE INVENTION
The problem addressed by the present invention was to provide self-dispersible curable epoxy resins. The expression “self-dispersible” in the context of the present invention means that the epoxy resins can be dispersed or emulsified spontaneously in aqueous medium without the use of additional additives, such as emulsifying or dispersing additives. In other words, the epoxy resins to be developed are those which would be capable of self-dispersion and/or self-emulsification in water. In the interests of simplicity, the term “self-dispersing” is used for this property throughout the present specification. Another problem addressed by the invention was to provide aqueous dispersions of self-dispersible curable epoxy resins which would be distinguished by high stability in storage under practical storage conditions. A further problem addressed by the invention was to provide coating compositions containing a self-dispersible curable epoxy resin, the coating obtained from the coating composition after the curing process being distinguished by excellent properties.
It has now surprisingly been found that epoxy resins obtainable by reaction of (a) 1.0 equivalent of epoxy resin, (b) 0.01 to 1.0 equivalent of a polyhydric phenol and (c) 0.005 to 0.5 equivalent of an amine/epoxy adduct, the amine/epoxy adduct being a reaction product of 1.0 equivalent of an aromatic polyepoxide and 0.10 to 0.28 equivalent of a polyoxyalkyleneamine, excellently satisfy the requirements mentioned in every respect.
The present invention relates first to self-dispersible curable epoxy resins obtainable by reaction of (a) 1.0 equivalent of epoxy resin, (b) 0.01 to 1.0 equivalent of a polyhydric phenol and (c) 0.005 to 0.5 equivalent of an amine/epoxy adduct, the amine/epoxy adduct (c) being a reaction product of an aromatic polyepoxide with a polyoxyalkyleneamine and the compounds used for the preparation of the amine/epoxy adduct (c), namely the aromatic polyepoxide and the polyoxyalkyleneamine, being used in an equivalent ratio of 1:0.10 to 1:0.28.
The expression “equivalent ratio” is familiar to the expert. The basic concept behind the notion of the equivalent is that, for every substance participating in a reaction, the reactive groups involved in the desired reaction are taken into consideration. By indicating an equivalent ratio, it is possible to express the ratio which all the various reactive groups of the compounds (x) and (y) used bear to one another. In the context of the invention, a reactive group is understood to be the functional group and not the smallest possible reactive group. In the case of amines containing NH
2
groups, this means for example that the NH
2
group is meant, not an NH unit.
It is specifically pointed out that the teaching of the present invention differs from the teaching of the above-cited WO 96/20971 in the special equivalent ratio selected in the production of component (c) from polyepoxide and polyoxyalkylenediamine. According to WO 96/20971, the polyepoxide and the polyoxyalkylenediamine should be used in an equivalent ratio of 1:0.3 to 1:0.9; according to the teaching of the present invention, the polyepoxide and the polyoxyalkylenediamine should be used in an equivalent ratio of 1:0.10 to 1:0.28. An equivalent ratio of 1:0.15 to 1:0.25 is preferred.
So far as components (a), (b) and (c) and their reaction are concerned, reference is explicitly made to the observations in WO 96/20971. Accordingly, the disclosure of WO 96/20971 is expressly included in the disclosure of the present invention.
Epoxy resins (a) in the context of the present invention—and in accordance with the above-cited WO 96/20971 (cf. page 13, line 10 to page 16, line 13)—are understood to be polyglycidyl ethers of polyhydric phenols. These compounds hav
Foglianisi Vincenzo
Huver Thomas
Leuschner Tamara
Sulzbach Horst
Aylward D.
Cognis Deutschland GmbH & Co. KG
Dawson Robert
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